.\" Copyright (C) 1996 Andries Brouwer (aeb@cwi.nl)
.\" and Copyright (C) 2016 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
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.\" Modified Thu Oct 31 14:18:40 1996 by Eric S. Raymond <esr@y\thyrsus.com>
.\" Modified 2001-12-17, aeb
.TH GETSID 2 2016-10-08 "Linux" "Linux Programmer's Manual"
.SH NAME
getsid \- get session ID
.SH SYNOPSIS
.B #include <unistd.h>
.sp
.BI "pid_t getsid(pid_t" " pid" );
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.ad l
.PD 0
.BR getsid ():
.RS 4
_XOPEN_SOURCE\ >=\ 500
.\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
.br
    || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
.RE
.PD
.ad
.SH DESCRIPTION
.I getsid(0)
returns the session ID of the calling process.
.BR getsid ()
returns the session ID of the process with process ID
.IR pid .
If
.I pid
is 0,
.BR getsid ()
returns the session ID of the calling process.
.SH RETURN VALUE
On success, a session ID is returned.
On error, \fI(pid_t)\ \-1\fP will be returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EPERM
A process with process ID
.I pid
exists, but it is not in the same session as the calling process,
and the implementation considers this an error.
.TP
.B ESRCH
No process with process ID
.I pid
was found.
.SH VERSIONS
This system call is available on Linux since version 2.0.
.\" Linux has this system call since Linux 1.3.44.
.\" There is libc support since libc 5.2.19.
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008, SVr4.
.SH NOTES
Linux does not return
.BR EPERM .

See
.BR credentials (7)
for a description of sessions and session IDs.
.SH SEE ALSO
.BR getpgid (2),
.BR setsid (2),
.BR credentials (7)
